In multipoint video conferences between multiple end-point conference sites, it is often desirable to open a point-to-point data channel or other data channel between conference participants. However, opening of a data channel can cause a communications bandwidth imbalance in conventional multipoint video conferencing systems. End-point units located at each non-participating conference site, which are not receiving data information via the data channel, may remain capable of sending and receiving more video information than participating end-point units, which are processing the data channel. Such a bandwidth imbalance can cause video buffer overruns and loss of frame synchronization in the control of the multipoint conference which in turn degrades video performance for all conference participants.
Another disadvantage of some conventional systems is that in order to open a data channel, a bitstream template is set and remains set throughout the multipoint conference so that the data bandwidth is set aside regardless of whether it is being used. It is desirable for a conference site to be allowed to open and close data channels between other conference sites without being forced to define the data channels initially and without consuming bandwidth when no data channel is needed.